Devices containing a remote phosphor package with red line emitting phosphors and green emitting quantum dots

ABSTRACT

A remote phosphor package according to the present invention includes a green emitting quantum dot material and a Mn 4+  doped phosphor of formula I, dispersed in a host matrix 
     
       
         
         
             
             
         
       
     
     wherein
         A is Li, Na, K, Rb, Cs, or combinations thereof;   M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Y, La, Nb, Ta, Bi, Gd, or combinations thereof;   x is an absolute value of a charge of the [MF y ] ion; and   y is 5, 6 or 7.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional of and claims priority from U.S.provisional application, Ser. No. 62/304,572, filed Mar. 7, 2016, theentire disclosure of which is incorporated herein by reference.

BACKGROUND

Energy efficiency is a critical feature in the field of consumerelectronics, and displays consume a large portion of device power.Display power consumption highly affects many features of electronicdisplay devices, including battery requirements in mobile displayapplications, as well as device operating temperature and panellifetime, especially in large display applications. In conventionaldisplay devices, a majority of the energy consumed by the device isdedicated to the display, particularly the display backlight unit.Conventional phosphors exhibit broad emission spectra, so a large amountof the light produced is filtered out by color filters to producesharper color components. This broad spectrum filtering results inwasted light energy, decreased brightness, and higher display operatingtemperatures. Therefore, improvements in color gamut and brightness aredesirable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a conventional liquid crystal display (LCD) with anedge lit backlight configuration.

FIG. 1B illustrates a direct lit backlight configuration for theconventional LCD.

FIG. 2 illustrates a backlight unit or module 200 according to thepresent invention.

FIG. 3 illustrates backlight unit according to the present invention.

BRIEF DESCRIPTION

It has been discovered that backlight units including a remote phosphorpackage according to the present invention exhibit efficiencyimprovements over conventional display backlight units due to theefficient use of primary light, resulting in a reduction in wasted lightenergy. The remote phosphor package includes a green emitting quantumdot material and a Mn⁴⁺ doped phosphor of formula I, dispersed in a hostmatrix

wherein

-   -   A is Li, Na, K, Rb, Cs, or combinations thereof;    -   M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Y, La, Nb, Ta, Bi, Gd,        or combinations thereof;    -   x is an absolute value of a charge of the [MF_(y)] ion; and    -   y is 5, 6 or 7.

DETAILED DESCRIPTION

FIG. 1A illustrates a conventional liquid crystal display (LCD) with anedge lit backlight configuration. LCD 100A includes a primary lightsource or backlight source 102, light guide panel 106, and a LCD panel120. The LCD 100 uses the LCD panel 120 with control electronics and thebacklight source 102 to produce color images. The backlight source 102provides white light.

The liquid crystal display panel 120 includes color filters 122 arrangedin subpixels, such as a red color filter, a green color filter, and ablue color filter. The red, green, and blue filters 122 transmit a lighthaving a specific wavelength of white light incident from the backlightsource 102. The filters 122 transmit wavelengths of light correspondingto the color of each filter, and absorb other wavelengths.

The LCD panel 120 also includes a front polarizer 118, a rear polarizer114, a thin film transistor 126, and liquid crystal 116 as well aselectrodes (not shown). The color filters 122 are positioned between theliquid crystal 116 and the front polarizer 118. The thin film transistor126 is positioned between the liquid crystal 116 and the rear polarizer114. Each pixel has a corresponding transistor or switch for controllingvoltage applied to the liquid crystal 116. The front and rear polarizers118 and 114 may be set at right angles. Normally, the LCD panel 120 isopaque. When a voltage is applied across the liquid crystal 116, therod-shaped polymers align with the electric field and untwist such thatthe voltage controls the light output from the front polarizer 118. Forexample, when a voltage is applied to the liquid crystal 116, the liquidcrystal 116 rotates so that there is a light output from the frontpolarizer 118.

Backlight source 102 includes one or more blue LEDs and yellow phosphorpumped by the blue LEDs to emit white light for LCD 100. The white lightfrom the backlight source 102 travels toward light guide panel 106,through diffuser film 110 and prism 108 as well as double brightnessenhanced film 124, which provides a uniform light backlight for theliquid crystal display panel 120. Alternatively, the backlight source102 may include a white LED that provides white light to the light guidepanel 106. The white LED may use a blue LED with broad spectrum yellowphosphor, or a blue LED with red and green phosphors.

FIG. 1B illustrates a direct lit backlight configuration for theconventional LCD. As shown, the main differences from the edge litconfiguration 100B include different arrangement of a number of LEDs andabsence of light guide panel 106. More specifically, the LEDs 102 arearranged to directly provide light to a diffuser plate 126, which isnormally thicker than the diffuser film 110 and thus supports thediffuser film 110.

FIG. 2 illustrates a backlight unit or module 200 according to thepresent invention that includes light source 202, light guide panel 204,remote phosphor package 206, dichroic filter 210, and LCD panel 216.Backlight unit 200 may also optionally include a prism 212 and a doublebrightness enhanced film 214. The light source 202 is a blue emittingLED. To produce even lighting, blue light from the light source 202first passes through light guide panel 204 which diffuses the bluelight. The LCD panel 216 also includes color filters arranged insubpixels, a front polarizer, a rear polarizer, and liquid crystal aswell as electrodes, similar to the LCD panel 120 for the conventionalLCD 100. Generally, there is an air space between the LCD panel 216 andthe double brightness enhanced film 214. The double brightness enhancedfilm 214 is a reflective polarizer film which increases efficiency byrepeatedly reflecting any unpolarized light back, which would otherwisebe absorbed by the LCD's rear polarizer. The double brightness enhancedfilm 214 is placed behind the liquid crystal display panel 216 withoutany other film in-between. The double brightness enhanced film 214 maybe mounted with its transmission axis substantially parallel to thetransmission axis of the rear polarizer. The double brightness enhancedfilm 214 helps recycle the white light 222 that would normally beabsorbed by the rear polarizer (not shown) of the liquid crystal panel216, and thus increases the brightness of the liquid crystal displaypanel 216.

It will be appreciated by those skilled in the art that a backlight unitaccording to the present invention may vary in configuration. Forexample, a direct lit configuration may be used, similar to the directlit configuration shown in FIG. 1B. The prism 212 may also be removed orsubstituted by other brightness enhancement component in an alternativeembodiment. The double brightness enhanced film 214 may be removed inanother embodiment.

Unlike the conventional LCD 100, instead of using the red phosphor 110Aand green phosphor 110B, remote phosphor package 206 includes particles208A of a complex fluoride phosphor of formula I and particles 208B of agreen quantum dot material. It is “remote” in the sense that the primarylight source and the phosphor material are separate elements, and thephosphor material is not integrated with the primary light source as asingle element. Primary light is emitted from the primary light sourceand is travels through one or more external media to radiationallycouple the LED light source to the QD-phosphor material.

Red-emitting phosphors based on complex fluoride materials activated byMn⁴⁺, such as those described in U.S. Pat. Nos. 7,358,542, 7,497,973,and 7,648,649, absorb blue light strongly, and efficiently emit betweenabout 610 nanometers and 635 nanometers with little deep red/NIRemission. The complex fluoride phosphors of formula I have a hostlattice containing a coordination center, surrounded by fluoride ionsacting as ligands, and charge-compensated by counter ions (A) asnecessary. For example, in K₂[SiF₆], the coordination center is Si andthe counter ion is K. Complex fluorides are occasionally represented asa combination of simple, binary fluorides but such a representation doesnot indicate the coordination number for the ligands around thecoordination center. The square brackets (occasionally omitted forsimplicity) indicate that the complex ion they encompass is a newchemical species, different from the simple fluoride ion. The Mn⁴⁺dopant or activator acts as an additional coordination center,substituting a part of the coordination center, for example, Si, forminga luminescent center. The host lattice (including the counter ions) mayfurther modify the excitation and emission properties of the activatorion.

The counter ion A in formula I is Li, Na, K, Rb, Cs, or combinationsthereof, and y is 6. In certain embodiments, A is Na, K, Rb, orcombinations thereof. The coordination center M in formula I is anelement selected from the group consisting of Si, Ge, Ti, Zr, Hf, Sn,Al, Ga, In, Sc, Y, Bi, La, Gd, Nb, Ta, and combinations thereof. Incertain embodiments, M is Si, Ge, Ti, or combinations thereof. Examplesof the phosphors of formula I include K₂[SiF₆]:Mn⁴⁺, K₂[TiF₆]:Mn⁴⁺,K₂[SnF₆]:Mn⁴⁺, Cs₂[TiF₆]:Mn⁴⁺, Rb₂[TiF₆]:Mn⁴⁺, Cs₂[SiF₆]:Mn⁴⁺,Rb₂[SiF₆]:Mn⁴⁺, Na₂[TiF₆]:Mn⁴⁺, Na₂[ZrF₆]:Mn⁴⁺, K₃[ZrF₇]:Mn⁴⁺,K₃[BiF₇]:Mn⁴⁺, K₃[YF₇]:Mn⁴⁺, K₃[LaF₇]:Mn⁴⁺, K₃[GdF₇]:Mn⁴⁺,K₃[NbF₇]:Mn⁴⁺, K₃[TaF₇]:Mn⁴⁺. In certain embodiments, the phosphor offormula I is K₂[SiF₆]:Mn⁴⁺.

QD materials for use in the remote phosphor package include at least onepopulation of QDs capable of emitting green light upon excitation by ablue light source. The QD wavelengths and concentrations can be adjustedto meet the optical performance required. Preferred QD characteristicsinclude high quantum efficiency (e.g., about 90% or greater), continuousand tunable emission spectrum, and narrow and sharp spectral emission,e.g., less than 40 nm, 30 nm or less, or 20 nm or less full width athalf max (FWHM).

The green emitting quantum dot material may include a group II-VIcompound, a group III V compound, a group IV-IV compound, a group IVcompound, a group I-III-VI₂ compound or a mixture thereof. Non-limitingexamples of group II-VI compounds include CdSe, CdTe, CdS, ZnSe, ZnTe,ZnS, HgTe, HgS, HgSe, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS,HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS,HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe,HgZnSeS, HgZnSeTe, HgZnSTe, or combinations thereof. Group III-Vcompounds may be selected from the group consisting of GaN, GaP, GaAs,AlN, AlP, AlAs, InN, InP, InAs, GaNP, GaNAs, GaPAs, AlNP, AlNAs, AlPAs,InNP, InNAs, InPAs, GaAlNP, GaAlNAs, GaAlPAs, GaInNP, GaInNAs, GaInPAs,InAlNP, InAlNAs, InAlPAs, and combinations thereof. Examples of group IVcompounds include Si, Ge, SiC, and SiGe. Examples of group I-III-VI₂chalcopyrite-type compounds include CuInS₂, CuInSe₂, CuGaS₂, CuGaSe₂,AgInS₂, AgInSe₂, AgGaS₂, AgGaSe₂ and combinations thereof.

QDs for use in the remote package may be a core/shell QD, including acore, at least one shell coated on the core, and an outer coatingincluding one or more ligands, preferably organic polymeric ligands.Exemplary materials for preparing core-shell QDs include, but are notlimited to, Si, Ge, Sn, Se, Te, B, C (including diamond), P, Co, Au, BN,BP, BAs, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs,InSb, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, ZnO, ZnS, ZnSe, ZnTe,CdS, CdSe, CdSeZn, CdTe, HgS, HgSe, HgTe, BeS, BeSe, BeTe, MgS, MgSe,MnS, MnSe, GeS, GeSe, GeTe, SnS, SnSe, SnTe, PbO, PbS, PbSe, PbTe, CuF,CuCl, CuBr, CuI, Si3N4, Ge3N4, Al2O3, (Al,Ga,In)2(S,Se,Te)3, Al2CO, andappropriate combinations of two or more such materials. Exemplarycore-shell QDs include, but are not limited to, CdSe/ZnS, CdSe/CdS,CdSe/CdS/ZnS, CdSeZn/CdS/ZnS, CdSeZn/ZnS, InP/ZnS, PbSe/PbS, PbSe/PbS,CdTe/CdS and CdTe/ZnS.

The QD materials typically include ligands conjugated to, cooperatedwith, associated with, or attached to their surface. In particular, theQDs may include a coating layer comprising ligands to protect the QDsfrom environmental conditions including elevated temperatures, highintensity light, external gasses, and moisture, control aggregation, andallow for dispersion of the QDs in the matrix material.

In some embodiments, a remote phosphor package according to the presentinvention may contain a narrow green emitting phosphor material insteadof or in addition to a quantum dot material. Examples of suitable greenemitting phosphors include CdS:In, SrGa₂S₄:Eu, CaSO₄:Bi, SrS:Mn, ZnS:Eu,and CaGa₂S₄:Eu.

The remote phosphor package material additionally includes a matrixmaterial in which the QD-phosphor material is embedded or otherwisedisposed. Suitable matrix materials are transparent, non-yellowing, andchemically and optically compatible with the backlight unit components,including the QDs and any surrounding packaging materials or layers.Preferred matrix materials have low oxygen and moisture permeability,exhibit high photo- and chemical-stability, exhibit favorable refractiveindices, and adhere to the barrier or other layers adjacent the QDphosphor material, thus providing an air-tight seal to protect theQD-phosphor material.

Examples of matrix materials for use in QD phosphor material of thepresent invention include epoxies, acrylates, norborene, polyethylene,poly(vinyl butyral):poly(vinyl acetate), polyurea, polyurethanes;silicones and silicone derivatives including, but not limited to, aminosilicone (AMS), polyphenylmethylsiloxane, polyphenylalkylsiloxane,polydiphenylsiloxane, polydialkylsiloxane, silsesquioxanes, fluorinatedsilicones, and vinyl and hydride substituted silicones; acrylic polymersand copolymers formed from monomers including, but not limited to,methylmethacrylate, butylmethacrylate, and laurylmethacrylate;styrene-based polymers such as polystyrene, amino polystyrene (APS), andpoly(acrylonitrile ethylene styrene) (AES); polymers that arecrosslinked with difunctional monomers, such as divinylbenzene;cross-linkers suitable for cross-linking ligand materials, epoxideswhich combine with ligand amines (e.g., APS or PEI ligand amines) toform epoxy polymers.

Referring to FIG. 3, backlight unit 300 according to the presentinvention includes backplane 2, light guide panel 4, LED light source 6,mounting bracket 8, and a remote phosphor package in the form of a strip10, mounted in the backplane 2. The remote phosphor package 10 ismounted via mounting bracket 8 between light guide panel 4 and LED lightsource 6, whereby light emitting from the backlight source 6 istransmitted through composite material 10 and then enters the lightguide plate 4. The backlight unit may further include a bottom reflectorplate 14 arranged between light guide panel 4 and the backplane 2 and anoptical film assembly 16 arranged above the light guide plate 4.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

1-15. (canceled)
 16. A backlight unit comprising an LED light source anda remote phosphor package radiationally coupled to an LED light source;the remote phosphor package comprising a green emitting quantum dotmaterial and a Mn⁴⁺ doped phosphor of formula I, dispersed in a hostmatrix, wherein the backlight unit is in the absence of a light guidepanel,A_(x)[MF_(y)]:Mn⁴⁺  I wherein A is Li, Na, K, Rb, Cs, or combinationsthereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Y, La, Nb, Ta, Bi Gd,or combinations thereof; x is an absolute value of a charge of the[Mf_(y)] ion; and y is 5, 6 or
 7. 17. The backlight unit of claim 16,wherein the backlight unit is in a direct lit backlight unitconfiguration.
 18. The backlight unit of claim 16, wherein the lightemitted by the LED light source travels through one or more mediaexternal to the remote phosphor package to radiationally couple the LEDlight source to the remote phosphor package.
 19. The backlight unit ofclaim 16, wherein the LED light source is directly arranged to providelight to a diffuser plate.
 20. The backlight unit of claim 19, whereinthe diffuser plate supports a diffuser film.
 21. The backlight unit ofclaim 16, wherein the color stable Mn⁴⁺ doped phosphor is K₂SiF₆:Mn⁴⁺.22. The backlight unit of claim 16, wherein the quantum dot materialcomprises CdSe or InP.
 23. An electronic device comprising a backlightunit according to claim
 16. 24. A display device comprising a backlightunit according to claim
 16. 25. A mobile display device comprising abacklight unit according to claim
 16. 26. A backlight unit comprising adevice, the device comprising an LED light source radiationally coupledto a green emitting quantum dot material and a Mn⁴⁺ doped phosphor offormula I,Ax[MF_(y)]:Mn⁴⁺  I the green emitting quantum dot material comprising agroup II-VI compound, a group III-V compound, a group IV compound, agroup I-III-VI₂ compound of or a mixture thereof; wherein the backlightunit is in the absence of a light guide panel; and wherein A is Li, Na,K, Rb, Cs, or combinations thereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In,Sc, Y, La, Nb, Ta, Bi Gd, or combinations thereof; x is an absolutevalue of a charge of the [Mf_(y)] ion; and y is 5, 6 or
 7. 27. Thebacklight unit of claim 26, wherein the color stable Mn⁴⁺ doped phosphoris K₂SiF₆:Mn⁴⁺.
 28. The backlight unit of claim 26, wherein the quantumdot material comprises CdSe or InP.
 29. An electronic device comprisinga backlight unit according to claim
 26. 30. A display device comprisinga backlight unit according to claim
 26. 31. A mobile display devicecomprising a backlight unit according to claim
 26. 32. A backlight unitcomprising an LED light source and a remote phosphor packageradiationally coupled to an LED light source; the remote phosphorpackage comprising a green emitting quantum dot material and a Mn⁴⁺doped phosphor of formula I, dispersed in a host matrix, wherein thebacklight unit lacks a light guide panel,A_(x)[MF_(y)]:Mn⁴⁺  I wherein A is Li, Na, K, Rb, Cs, or combinationsthereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Y, La, Nb, Ta, Bi Gd,or combinations thereof; x is an absolute value of a charge of the[Mf_(y)] ion; and y is 5, 6 or
 7. 33. The backlight unit of claim 32,wherein the color stable Mn⁴⁺ doped phosphor is K₂SiF₆:Mn⁴⁺.
 34. Thebacklight unit of claim 32, wherein the quantum dot material comprisesCdSe or InP.
 35. The backlight unit of claim 32, wherein the LED lightsource is directly arranged to provide light to a diffuser plate.